Porous metal implants are used to promote ingrowth of surrounding bony tissue and soft tissues into the implant. When the porosity, integrity and continuity of the metals are sufficient, porous implants serve as a scaffold for tissue ingrowth to provide the desired load-bearing strength to the implant site.
The porous implants can be formed by removing pieces from a metal substrate, such as by etching a solid piece of metal. The implants can also be formed by using small metal particles such as powders. Where metal powders are used, multi-step heat and pressure application steps can compromise the desired integrity and load-bearing strength of the implant due to shifts in the structure during initial molding and when transferring the implant between the various furnaces, pressure chambers, machining apparatus, etc. Furthermore, temperatures and pressures must accommodate the removal of foaming agents or spacing agents without further compromising the implant. These multiple considerations in forming the implant limit the formation of complex shapes from the starting materials because switching between the various pressing, heating, shaping, and other processing steps can cause the implant to become misshapen. In other systems using metal powders, a binding or interface layer must be used in order to attach the porous structure to a substrate. Many of these methods use different metals to form the substrate and the porous layer, leading to corrosion and a reduction in the life span of the implant.
It may be desirable to provide a porous metal implant which has one or more of these properties: a desirable porosity, is shaped and processed easily, readily forms three-dimensional complex shapes, maintains its intended shape throughout the various processing steps, promotes soft and hard tissue ingrowth, and is suitable for load-bearing applications.